Voice service in evolved packet system

ABSTRACT

Methods and apparatus to manage voice service in evolved packet systems are disclosed. An example method in a User Equipment (UE) includes receiving a Non Access Stratum (NAS) protocol response message with a first indicator, the first indicator provided by lower layers of the UE to upper layers of the UE, responsive to the first indicator, initiating an IMS registration if the UE is not already registered with the IMS, and responsive to the UE having registered with the IP Multimedia (IM) Core Network (CN) Subsystem (IMS), determining availability of voice services over the IP Multimedia (IM) Core Network (CN) Subsystem (IMS).

RELATED APPLICATIONS

This patent is a continuation of U.S. patent application Ser. No.12/793,670, filed Jun. 3, 2010, entitled Voice Service in Evolved PacketSystem, which is a non-provisional of U.S. Provisional Application Ser.No. 61/183,935, filed Jun. 3, 2009, entitled “Voice Service in EvolvedPacket System Using IP Multimedia Subsystem.” U.S. patent applicationSer. No. 12/793,670 and U.S. Provisional Application Ser. No. 61/183,935are hereby incorporated by reference in their entirety.

FIELD OF THE DISCLOSURE

The application relates generally to mobile communication system and,more particularly, to the provision of voice services in Evolved PacketSystem.

BACKGROUND

Recently, Voice Service Indicators have been defined in evolved packetsystem (EPS) mobile communication systems to coordinate the availabilityof network services and capabilities of mobile devices. The voiceservice indicators include, for example:

-   -   “IMS Voice over PS session supported” indication;    -   “Voice Centric” or “Data Centric” indication; and    -   “CS Voice only” or “IMS PS voice only” or “CS voice preferred,        IMS voice secondary” or “IMS voice preferred, CS voice        secondary” indication.

The “IMS Voice over PS session Supported” indication is provided by thenetwork to the user equipment (UE) (given in non access stratum (NAS)registration (e.g. EPS attach) or NAS registration update). The “VoiceCentric” or Data Centric” indication and the “CS Voice Only,” “IMS PSvoice only,” “CS voice preferred, IMS voice secondary,” or “IMS Voicepreferred, CS voice secondary” indication is available on the UE. Anoperator can configure the “CS Voice Only,” “IMS PS voice only,” “CSvoice preferred, IMS voice secondary,” or “IMS Voice preferred, CS voicesecondary” indication on the UE.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the various implementations describedherein and to show more clearly how they may be carried into effect,reference will now be made, by way of example only, to the accompanyingdrawings which show at least one example implementation and in which:

FIGS. 1A, 1B, 2A, 2B, 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 7C, 7D,8A, 8B, 9A, 9B, 10A, 10B, 10C, 11A, 11B, 11C, 11D, and 11E areflowcharts illustrating example operation of a UE described herein.

FIG. 12 is a block diagram of a mobile communication device that mayimplement UE related methods described herein.

DETAILED DESCRIPTION

Abbreviations and Terminology AS Access Stratum CN Core Network CSCircuit Switched CSFB CS Fallback EMM Evolved Packet System (EPS)Mobility Management eNB eNodeB EPC Evolved Packet Core EPS EvolvedPacket System E-UTRAN Evolved UTRAN IMS IP Multimedia Subsystem IM CN IPMultimedia Core Network MAC Medium Access Control MS Mobile Station NASNon Access Stratum NW Network PS Packet Switched RA Routing Area PDCPPacket Data Convergence Protocol RAN Radio Access Network RAU RoutingArea Update RB Radio Bearer RLC Radio Link Control RRC Radio ResourceControl TA Tracking Area TAI TA Identity TAU Tracking Area Update TSTechnical Specification UE User Equipment UMTS Universal MobileTelecommunications System UTRAN UMTS Terrestrial RAN VoIMS Voice overIMS

In example implementation described herein, the voice service indicatorsmay be Network provided VoIMS indicators, UE usage settings, and UserEquipment voice settings. In the following description, voice serviceindicators are referred to as:

a) (Network provided) (IMS) VoIMS indicator indicating the abovereferenced “IMS Voice over PS session supported” indication or abovereferenced “IMS Voice over PS session not supported” indication, andindicates if voice over PS sessions controlled and managed by the IPmultimedia subsystem is or is not supported;

b) UE's usage setting indicating the above-referenced “Voice Centric” or“Data Centric”. The UE usage setting is a UE setting that indicateswhether the UE has a preference for voice services over data services orvice-versa. If UE has preference for voice services, then the UE's usagesetting is “Voice Centric”. If a UE has a preference for data services,then the UE's usage setting is “Data Centric”. For avoidance of doubt aUE that is “Data Centric” may still require voice services. If a UErequires only data services and can accept that there is no voiceservice, the UE's usage setting is “Data Only.” The two settings mayhave the following meanings:

-   -   “Voice Centric”: a Voice Centric UE must be able to use voice        services, and therefore will attempt to obtain voice services        independently of how such services can be provisioned    -   “Data Centric”: a Data Centric UE prefers to have the best        possible PS services even if this implies no access to voice        services is possible

A further UE's usage setting of “Data Only” is possible. In the casethat this additional setting is possible then the three settings mayhave the following meanings:

-   -   “Voice Centric”: a Voice Centric UE must be able to use voice        services, and therefore will attempt to obtain voice services        independently of how such services can be provisioned    -   “Data Centric”: a Data Centric UE prefers to have the best        possible PS services (i.e. prefers to stay in E-UTRAN) provided        that access to voice service is not excluded    -   “Data Only”: a Data Centric UE prefers to have the best possible        PS services even if this implies no access to voice services is        possible; and

c) UE's voice setting indicating the above-referenced “CS Voice Only”,“PS Voice Only”, “IMS PS Voice Only”, “CS Voice Preferred, IMS VoiceSecondary”, or “IMS Voice Preferred, CS Voice Secondary” indications.The UE voice setting is a UE setting that indicates the domain to usefor voice services.

Table 1 summarizes this grouping and naming convention.

TABLE 1 Description of Voice Indicators Generic Name of Indicator usedin this Name Ownership of Application of Indicators in theSpecifications indicators VoIMS “IMS Voice over PS session not Set byNW. indicator supported” or Provided by NW “IMS Voice over PS session toUE in response supported” to each NAS registration (e.g. EPS attach) orNAS registration update UE's usage “Voice centric” or Could be setting“Data centric” or provisioned by “Data only” Operator or could bechanged by the UE for example as a result of user input. UE's voice “CSVoice only” or Could be setting “IMS PS voice only” or provisioned by“CS voice preferred, IMS voice Operator or could secondary” or bechanged by the “IMS voice preferred, CS voice UE for example secondary”as a result of user input.

In an example implementation, a network message may include a VoIMSindicator. For example, an ATTACH ACCEPT message in accordance with 3GPPTS 24.301 may be implemented as shown in Table 2 and/or in Iu mode inaccordance with 3GPP TS 24.008 shown in Table 3. The VoIMS indicator maybe sent by the network to a UE to indicate the support of voice viasessions of the IMS.

TABLE 2 ATTACH ACCEPT 3GPP TS 24.301 IEI Information ElementType/Reference Presence Format Length Protocol discriminator Protocoldiscriminator M V ½ 9.2 Security header type Security header type M V ½9.3.1 Attach accept message identity Message type M V 1 9.8 EPS attachresult EPS attach result M V ½ 9.9.3.10 Spare half octet Spare halfoctet M V ½ 9.9.2.9 T3412 value GPRS timer M V 1 9.9.3.16 TAI listTracking area identity list M LV 7-97 9.9.3.33 ESM message container ESMmessage container M LV-E 2-n  9.9.3.15 50 GUTI EPS mobile identity O TLV13  9.9.3.12 13 Location area identification Location areaidentification O TV 6 9.9.2.2 23 MS identity Mobile identity O TLV 7-109.9.2.3 53 EMM cause EMM cause O TV 2 9.9.3.9 17 T3402 value GPRS timerO TV 2 9.9.3.16 59 T3423 value GPRS timer O TV 2 9.9.3.16 4A EquivalentPLMNs PLMN list O TLV 5-47 9.9.2.8 34 Emergency Number List EmergencyNumber List O TLV 5-50 9.9.3.37 39 VoIMS indicator VoIMS indicator O TV1 9.9.x.y

TABLE 3 ATTACH ACCEPT 3GPP TS 24.008 IEI Information ElementType/Reference Presence Format Length Protocol discriminator Protocoldiscriminator M V ½ 10.2 Skip indicator Skip indicator M V ½ 10.3.1Attach accept message identity Message type M V 1 10.4 Attach resultAttach result M V ½ 10.5.5.1 Force to standby Force to standby M V ½10.5.5.7 Periodic RA update timer GPRS Timer M V 1 10.5.7.3 Radiopriority for SMS Radio priority M V ½ 10.5.7.2 Radio priority for TOM8Radio priority 2 M V ½ 10.5.7.5 Routing area identification Routing areaidentification M V 6 10.5.5.15 19 P-TMSI signature P-TMSI signature O TV4 10.5.5.8 17 Negotiated READY timer GPRS Timer O TV 2 value 10.5.7.3 18Allocated P-TMSI Mobile identity O TLV 7 10.5.1.4 23 MS identity Mobileidentity O TLV 7-10 10.5.1.4 25 GMM cause GMM cause O TV 2 10.5.5.14 2AT3302 value GPRS Timer 2 O TLV 3 10.5.7.4 8C Cell Notification CellNotification O T 1 10.5.5.21 4A Equivalent PLMNs PLMN List O TLV 5-4710.5.1.13 B- Network feature support Network feature support O TV 110.5.5.23 34 Emergency Number List Emergency Number List O TLV 5-5010.5.3.13 A- Requested MS Information Requested MS Information O TV 110.5.5.25 37 T3319 value GPRS Timer 2 O TLV 3 10.5.7.4 38 T3323 valueGPRS Timer 2 O TLV 3 10.5.7.4 39 VoIMS indicator VoIMS indicator O TV 1

As described herein, a UE has multiple protocol layers. An example UE,described herein includes 3 layers (IMS layer, NAS layer, and an ASlayer). The example ordering is as follows: IMS is above the NAS and ASlayers and the AS layer is a lower layer to the NAS and IMS layer.Therefore, the NAS layer and/or AS layer may be referred to as “lowerlayers” from the perspective of the IMS layer. The IMS layer may bereferred to as an upper layer.

In some example implementations, after completion of an attach procedurein, for example, Iu mode, if the VoIMS indicator is available in theATTACH ACCEPT message and indicates “IMS Voice over PS sessionsupported” the successful completion of the attach procedure will beindicated to the upper layers, for example, for initiation of SIPregistration to the IP Multimedia subsystem. Is some further exampleimplementations, the successful completion of the attach procedures isindicated to the upper layer subject to the UE's voice setting being setto, for example, one of “PS Voice Only” or “IMS Voice Preferred, CSVoice Secondary”.

In another example implementation, a TRACKING AREA UPDATE message inaccordance with 3GPP TS 24.301 may be implemented as shown in Table 4.

FIG. 4: TRACKING AREA UPDATE IEI Information Element Type/ReferencePresence Format Length Protocol discriminator Protocol discriminator M V½ 9.2 Security header type Security header type M V ½ 9.3.1 Trackingarea update accept Message type M V 1 message identity 9.8 EPS updateresult EPS update result M V ½ 9.9.3.13 Spare half octet Spare halfoctet M V ½ 9.9.2.9 5A T3412 value GPRS timer O TV 2 9.9.3.16 50 GUTIEPS mobile identity O TLV 13  9.9.3.12 54 TAI list Tracking areaidentity list O TLV 8-98 9.9.3.33 57 EPS bearer context status EPSbearer context status O TLV 4 9.9.2.1 13 Location area identificationLocation area identification O TV 6 9.9.2.2 23 MS identity Mobileidentity O TLV 7-10 9.9.2.3 53 EMM cause EMM cause O TV 2 9.9.3.9 17T3402 value GPRS timer O TV 2 9.9.3.16 59 T3423 value GPRS timer O TV 29.9.3.16 4A Equivalent PLMNs PLMN list O TLV 5-47 9.9.2.8 8- NAS key setidentifier_(ASME) NAS key set identifier O TV 1 9.9.3.21 34 EmergencyNumber List Emergency Number List O TLV 5-50 9.9.3.37 39 VoIMS indicatorVoIMS indicator O TV 1 9.9.x.y

In some example implementations in, for example, Iu mode, uponsuccessful completion of the tracking area update procedure, the VoIMSindicator if received in the TRACKING AREA UPDATE ACCEPT message shallbe indicated to the upper layers.

A ROUTING AREA UPDATE ACCEPT message may be sent by the network to theUE to provide the UE with GPRS mobility management related data inresponse to a ROUTING AREA UPDATE REQUEST from the UE. The ROUTING AREAUPDATE ACCEPT message, if received or provided to the UE, in accordancewith, for example, 3GPP TS 24.008, may include a VoIMS indicator asshown in Table 5.

TABLE 5 ROUTING AREA UPDATE ACCEPT 3GPP TS 24.008 IEI InformationElement Type/Reference Presence Format Length Protocol discriminatorProtocol discriminator M V ½ 10.2 Skip indicator Skip indicator M V ½10.3.1 Routing area update accept Message type M V 1 message identity10.4 Force to standby Force to standby M V ½ 10.5.5.7 Update resultUpdate result M V ½ 10.5.5.17 Periodic RA update timer GPRS Timer M V 110.5.7.3 Routing area identification Routing area identification M V 610.5.5.15 19 P-TMSI signature P-TMSI signature O TV 4 10.5.5.8 18Allocated P-TMSI Mobile identity O TLV 7 10.5.1.4 23 MS identity Mobileidentity O TLV 7-10 10.5.1.4 26 List of Receive N-PDU Numbers ReceiveN-PDU Number list O TLV 4-19 10.5.5.11 17 Negotiated READY timer valueGPRS Timer O TV 2 10.5.7.3 25 GMM cause GMM cause O TV 2 10.5.5.14 2AT3302 value GPRS Timer 2 O TLV 3 10.5.7.4 8C Cell Notification CellNotification O T 1 10.5.5.21 4A Equivalent PLMNs PLMN List O TLV 5-4710.5.1.13 32 PDP context status PDP context status O TLV 4 10.5.7.1 B-Network feature support Network feature support O TV 1 10.5.5.23 34Emergency Number List Emergency Number List O TLV 5-50 10.5.3.13 35 MBMScontext status MBMS context status O TLV 2-18 10.5.7.6 A- Requested MSInformation Requested MS Information O TV 1 10.5.5.25 37 T3319 valueGPRS Timer 2 O TLV 3 10.5.7.4 38 T3323 value GPRS Timer 2 O TLV 310.5.7.4 39 VoIMS indicator VoIMS indicator O TV 1 10.5.x.y

In, for example, Iu mode, the network may include the VoIMS indicator ina ROUTING AREA UPDATE ACCEPT message (or any other message) to indicatethe support of voice via sessions of the IMS.

In another example, the combined routing area updating procedure isinitiated by a GPRS MS operating in MS operation modes A or B, if the MSis in state GMM-REGISTERED and MM-IDLE, and if the network operates innetwork operation mode I and if in Iu mode, when the UE receives anindication from the upper layers that the SIP registration to the IPMultimedia subsystem has failed and subject to the UE's usage settingbeing set to, for example, “Voice Centric”.

In some implementations, after completion of an attach procedure or aregistration update procedure in accordance with, for example, 3GPP TS24.008, access to an IM CN may be initiated. For example, access may beinitiated in accordance with 3GPP TS 24.229 section 6.2 B.2.2.1. Forexample, the access to the IM CN may be initiated when the UE is notalready registered to the IM CN subsystem and the UE's usage setting isnot “Voice Centric.” In another example, the access to the IM CN may beinitiated when the UE is not already registered to the IM CN subsystemand the UE's voice setting is “PS Voice Only” or the UE's voice settingis “IMS Voice Preferred, CS Voice Secondary.” In yet another example, anindication of IM CN subsystem registration failure may be provided tothe lower layers under the following conditions:

if registration to the IM CN subsystem fails; or

if, after failing repeated attempts to register to the IM CN sybsystem,the UE reaches a pre-set number of retries and terminates furtherattempts; or

if after failing repeated attempts to register, the user aborts furtherattempts to register to IM CN subsystem

if a user initiated de-registration is performed; or

if the UE is explicitly or implicitly deregistered by the network.

In some implementations, the UE may perform actions upon NAS indicationto select specific RATs. In some implementations, when a UE receives amessage that includes an information element for “Capability UpdateRequirement” and an information element for “System specific capabilityupdate requirement list” is included, then for each of the RAT requestedin a “UE system specific capability” information element, if the UEsupports the listed RAT, the UE may:if the listed RAT is E-UTRAN and theNAS has not provided an indication to AS to select GERAN or UTRAN or thelisted RAT is not E-UTRAN, include the inter-RAT radio accesscapabilities for the listed RAT in the IE “UE system specificcapability” from the variable UE_CAPABILITY_REQUESTED. Additionally, ifthe listed RAT is GSM and PS Handover to GPRS is supported, include theIE “MS Radio Access Capability” in the variable UE_CAPABILITY_REQUESTED.

In some further implementations, the UE may perform actions upon NASindication to select specific RATs. In some implementations, whenperforming cell selection when leaving RRC_CONNECTED state, ontransition from RRC_CONNECTED to RRC_IDLE as a result of a NASindication to select GERAN or UTRAN, the UE may perform cell selectionon GERAN and UTRAN RATs and disable cell selection and reselection toE-UTRAN cells. Similarly, if NAS provides an indication to AS to selectGERAN or UTRAN while the UE is in RRC_IDLE, the UE shall perform cellselection on GERAN and UTRAN RATs and enable cell selection andreselection to E-UTRA cells.

In some further implementations, when performing cell selection whenleaving RRC_CONNECTED state, on transition from RRC_CONNECTED toRRC_IDLE as a result of a NAS indication to select GERAN or UTRAN, theUE shall perform cell selection on GERAN and UTRAN RATs and disable cellselection and reselection to E-UTRA cells. If NAS provides to the AS anindication to select GERAN or UTRAN, while the UE is in RRC_IDLE, the UEshall perform cell selection on GERAN and UTRAN RATs and disable cellselection and reselection to E-UTRA cells.

If NAS provides an indication to AS to select GERAN or UTRAN while theUE is in RRC_CONNECTED, the UE may perform the following action uponleaving RRC_CONNECTED, with a release cause of ‘other’:

reset MAC;

stop all timers that are running except T320;

release all radio resources, including release of the RLC entity, theMAC configuration and the associated PDCP entity for all establishedRBs;

indicate the release of the RRC connection to upper layers together withthe release cause;

if leaving RRC_CONNECTED was not triggered by reception of theMobilityFromEUTRACommand message:

-   -   enter RRC_IDLE by performing cell selection in accordance with        the cell selection process, defined for the case of leaving        RRC_CONNECTED, for example, as specified in 3GPP TS 36.304;

FIGS. 1A and 1B respectively show Figure A.2.1-1 and Figure A.4-1 ofS2-094178 [iii], and illustrate two use case scenarios. The first usecase is when the UE's voice setting is set to “IMS voice preferred, CSvoice secondary” and the second use case is when the UE's voice settingis set to “IMS voice only”. These figures indicate the required UEactions for different combinations of the network's VoIMS indicator andthe UE's usage setting.

Referring first to FIG. 1A, the behavior for the UE's voice setting of“IMS voice preferred, CS voice secondary” begins at block 1A-1 whichsimply shows that the UE's voice setting is set to IMS voice preferred,CS voice secondary. In block 1A-2, the UE initiates an EPS attachprocedure (non combined). In block 1A-3, the UE checks for the IMS voicesupported indication from the network, which is received as part of theresponse to the EPS attach procedure. If IMS voice is supported, then inblock 1A-4, the UE uses IMS voice. While attached to the system, the UEmay perform a Tracking Area Update (TAU) either periodically or when toUE moves to a different Tracking Area (TA). When performing the TAU theUE may receive a new VoIMS indicator in which case the UE processingreturns to the block 1A-3 where the VoIMS indicator is checked. If IMSvoice is not supported, then in block 1A-5, the UE performs the combinedTA/LA Update Procedure (also referred to as the combined TAU) for CSFBas in TS 23.272. If there is success, then in block 1A-6, the UE staysin E-UTRAN and uses CSFB if it requires voice services. Upon successfulcompletion of the tracking area update procedure, a VoIMS indicatorreceived in the TRACKING AREA UPDATE ACCEPT message shall be indicatedto the upper layers. On the other hand, if there is failure, then inblock 1A-7, the UE checks the UE's usage setting for “Voice centric” or“Data centric” setting. If the setting is data centric, then in block1A-8, the UE stays in the current RAT (E-UTRAN). On the other hand, ifthe setting is voice centric, then in block 1A-9, the UE selects anotherRAT in which it may obtain voice services.

A combined registration procedure such as a Combined Attach Procedure ora Combined Tracking Area Update refers to a single NAS registrationprocedure that is used to attempt to register for both PS services andCS services, where the CS voice service is provided on E-UTRAN by meansof CS Fall back (CSFB). For example, a UE operating in CS/PS mode 1 orCS/PS mode 2, in the EMM-REGISTERED state, shall initiate the combinedtracking area updating procedure when, for example, the UE receives anindication from the upper layers that the SIP registration to the IMShas failed and the UE's usage setting is “Voice Centric.” An example ofa Combined Attach Procedure or a Combined Tracking Area Update can befound in 3GPP TS 24.301.

Success of a combined registration procedure means that the UE isregistered for both PS and CS services. Failure of a combined proceduremeans that the UE is registered for PS services but not for CS services.For example, such a failure may be indicated to the UE by the networksending a Tracking Area Update Accept or Attach Accept message with anindication or cause value set to ‘CS domain not available’ or a valueindicating that the PS domain is not available. In addition there may beother failures, such as a failure where the UE is not registered for CSor PS services.

As a result of a NAS registration procedure or an EPS attach procedure,a UE initiating the procedures is registered with the network. As aresult of this NAS registration, the UE and the network obtaininformation enabling the sending of and the receiving of (IP) messagesas part of the Non-access stratum protocols. The UE and the network cansend and receive these (IP) messages. The obtained information in the UEand the network may need updating. The obtained information can beperiodically updated (e.g. due a timer expiring) or explicitly updated.A NAS registration can be a combined or a non-combined NAS registration,a successful combined NAS registration cause a UE to be registered forEPS services and non-EPS services.

As used herein, EPS services may be GPRS services in accordance with3GPP TS 24.008. Non-EPS services are services provided by a CS domain.As used herein, non-EPS services may be non-GPRS services in accordancewith 3GPP TS 24.008. A UE which camps on E-UTRAN can attach to both EPSservices and non-EPS services. Non-access stratum (NAS) protocols areprotocols between UE and mobile switching center (MSC) or serving GRPSsupport node (SGSN) that are not terminated in the UTRAN, and theprotocols between UE and MME that are not terminated in the E-UTRAN.

In one implementation, a UE initiating a NAS registration (e.g., acombined NAS registration) procedure can send at least one of an ATTACHREQUEST (e.g., a combined ATTACH REQUEST) message or Tracking AreaUpdate Request (e.g., a combined Tracking Area Update Request) message.Subsequent to sending the message, the UE can receive at least one of anATTACH ACCEPT (e.g., a combined ATTACH ACCEPT) message or Tracking AreaUpdate Request (e.g., a combined Tracking Area Update Request) message.

In one implementation, a UE updating the NAS registration (e.g. combinedNAS registration) information may include an update of the routing areainformation when using the Non-access stratum protocols between the UEand the SGSN or updating the tracking area information when using theNon-access stratum protocols between the UE and the MME or updating theinformation when using the Non-access stratum protocols between the UEand the MSC. A UE updating the NAS registration (e.g. combined NASregistration) information can send at least one of a TRACKING AREAUPDATE (e.g., combined TRACKING AREA UPDATE), a ROUTING AREA UPDATE(e.g., a combined ROUTING AREA UPDATE). Subsequent to sending themessage, the UE can receive at least one of a TRACKING AREA UPDATE(e.g., a combined TRACKING AREA UPDATE) (ACCEPT) response, a ROUTINGAREA UPDATE (e.g., a combined ROUTING AREA UPDATE) (ACCEPT) response.After successful updating the NAS registration (e.g. combined NASregistration) information, a UE is registered for EPS services andnon-EPS services.

In one implementation, after performing the NAS registration procedure,the UE can request a service from the network. The UE then sends aservice request (e.g., an extended service request) message to thenetwork. For example, in order to perform CSFB, the UE is registered forEPS services and non-EPS services, and the UE sends an extended servicerequest NAS protocol message. The UE can receive a SERVICE REJECTmessage in response.

For example, in some implementations, when a UE receives an ATTACHACCEPT message with EMM cause value #18 indicative of “CS domain notavailable,” the UE may perform the following actions in accordance with3GPP TS 24.301:

-   -   The UE shall stop timer T3410 if still running, shall reset the        tracking area updating attempt counter, shall set the EPS update        status to EU1 UPDATED and shall enter state        EMM-REGISTERED.NORMAL-SERVICE.    -   The UE shall set the update status to U2 NOT UPDATED.    -   A UE in CS/PS mode 1 of operation may select GERAN or UTRAN        radio access technology rather than E-UTRAN for the selected        PLMN or equivalent PLMN.    -   A UE in CS/PS mode 2 of operation shall not attempt combined        attach or combined tracking area update procedure with current        PLMN until switching off the UE or the UICC containing the USIM        is removed.    -   A UE whose UE's usage setting is “Data Centric” or “Data Only”        will provide a notification to the user or the upper layers that        CS domain is not available.    -   If the UE's usage setting is changed from “Data Centric” or        “Data Only” to “Voice Centric,” an indication shall be provided        to the AS to select GERAN or UTRAN radio access technology        rather than E-UTRAN for the selected PLMN or equivalent PLMN.

In some implementations, when a NAS provides an indication to an AS toselect GERAN or UTRAN while the UE is in RRC_IDLE, the UE may disablecell selection and reselection to E-UTRAN cells. When a NAS provides anindication to an AS to select GERAN or UTRAN or E-UTRAN while the UE isin RRC_IDLE, the UE may enable cell selection and reselection to E-UTRANcells.

In another example, if a service request cannot be accepted by thenetwork, the network will return a SERVICE REJECT message to the UEincluding an appropriate EMM cause value. On receipt of the SERVICEREJECT message, the UE shall stop timer T3417 and take appropriateaction. For example, the EMM cause value may be #18 (CS domain notavailable). If the request was related to CS fallback, the UE shall sendan indication to the MM sublayer and shall not attempt CS fallback untila combined tracking area updating procedure has been successfullycompleted. The UE may then enter the stateEMM-REGISTERED.NORMAL-SERVICE. If the UE usage setting is “Data Centric”or “Data Only,” the UE will provide a notification to the user or theupper layers that CS domain is not available.

Referring now to FIG. 1B, the behavior for UE voice setting of “IMS PSVoice only” begins at block 1B-1 which simply shows the UE set to IMS PSvoice only. In block 1B-2, the UE initiates an EPS attach procedure (noncombined). In block 1B-3, the UE checks for the IMS voice supportedindication from the network. If IMS voice is supported, then in block1B-4, the UE uses IMS voice. While attached to the system to UE mayperform a Tracking Area Update either periodically or when to UE movesto a different Tracking Area. When performing the TAU the UE may receivea new VoIMS indicator in which case the UE processing returns to theblock 1B-3 where the VoIMS indicator is checked. If IMS voice is notsupported, then in block 1B-5, UE checks the UE's usage setting for“Voice centric” or “Data centric”. If the setting is “Data centric”,then in block 1B-6, the UE stays in the current RAT (E-UTRAN). On theother hand, if the setting is “Voice centric, then in block 1B-7, the UEselects another RAT in which it may obtain voice services.

First Problem: Failure to Initiate IMS Registration

A first problem with the behavior specified in the above-referenced FIG.1A and FIG. 1B is that there is no guarantee that the UE will initiateIMS registration. More specifically, if the VoIMS indicator indicates“IMS Voice over PS session supported” then the UE is expected to “useIMS Voice”, but there is no guarantee that the UE will definitelyinitiate an IMS registration when the UE's voice setting is set to “IMSPS voice only” and “IMS voice preferred, CS voice secondary”. If theVoIMS indicator shows “IMS Voice over PS session supported”, then the UEknows that there is no NAS or AS reason that would mean it cannotrealize voice services over IMS. However, in order for this to beachieved, the UE must first initiate an IMS registration.

The reference to an IMS Registration to an IMS Subsystem can generallybe understood to refer to any method of the network obtaininginformation required in order to be able to send information to, andreceive information from the UE using IMS. Accordingly, the networkeither has obtained the information required in order to be able to sendinformation to, and receive information from the UE using IMS, or thenetwork does not have the information. A network may not have saidinformation due to registration failure or due to the UE having failedto register (e.g. the UE not having initiated an IMS registration toprovide the network with said information). A SIP Registration for voiceservices to an IMS Subsystem, as per 3GPP TS 24.229 is a specificexample.

When performing an IMS Registration for voice services, the UE mustinclude proper indicator(s) such that the IMS Subsystem knows that it isrequesting voice services. If a proper indicator is not included orgranted, then a UE camping on an IMS capable E-UTRAN cell will still notreceive IMS voice services or IMS voice mobile terminated sessionrequests.

In some implementations, in order to ensure that the UE reactsappropriately and initiates an IMS Registration, the UE will behave asfollows:

-   -   If UE's voice setting=“IMS PS voice only” OR    -   If UE's voice setting=“IMS voice preferred, CS voice secondary”    -   AND the VoIMS Indicator indicates “IMS Voice over PS session        supported”;    -   THEN IMS registration will be triggered with proper indicator(s)        requesting voice service support.

For example, upon successful completion of an attach procedure, if theVoIMS indicator in an ATTACH ACCEPT message indicates “IMS Voice over PSsession supported” and subject to the UE's voice setting the successfulcompletion of the attach procedure will be indicated to the upper layersfor initiation of SIP registration to the IMS.

As indicated above, in some implementations, the IMS registration isachieved through a SIP registration. Examples of SIP messages are SIPRequests and SIP Responses. Examples of a SIP Request is a SIP INVITE ora SIP REGISTER. Examples of IMS functional elements are P-CSCF, S-CSCF,I-CSCF, AS, SCC AS, HSS.

IMS Registration can be performed using a SIP Register request asdescribed in IETF RFC 3261; the SIP Register requests are processed byan IMS functional element as documented in 3GPP TS 23.228 and 3GPP TS24.229.

FIG. 2A shows a detailed flowchart of an example implementation for thecase where the UE's voice setting is set to “IMS voice preferred, CSvoice secondary”. The figure differs from FIG. 1A in the inclusion ofblock 2A-1 which involves attempting IMS registration with properindicators for voice services. In the case that the UE uses IMS voice atblock 1A-4 and then performs a TAU then the UE will again check theVoIMS indicator at block 1A-3 and if VoIMS is supported then at block2A-1 the UE will only attempt IMS Registration with proper indicatorsfor voice services if it is not already IMS registered for voiceservices.

FIG. 2B shows a detailed flowchart of an example implementation for thecase where the UE voice setting is set to “IMS PS voice only”. Thefigure differs from FIG. 1B in the inclusion of block 2B-1 whichinvolves attempting IMS registration with proper indicators for voiceservices. In the case that the UE uses IMS voice at block 1B-4 and thenperforms a TAU then the UE will again check the VoIMS indicator at block1B-3 and if VoIMS is supported then at block 2B-1 the UE will onlyattempt IMS Registration with proper indicators for voice services if itis not already IMS registered for voice services.

Second Problem: IMS Registration for Voice May Fail

A second problem with the behavior described above with reference toFIGS. 1A and 1B is that there is no guarantee IMS registration for voicewill succeed. More specifically, there is no guarantee that the IMSregistration for voice will succeed, just because EPS attach or TrackingArea Update is successful and the network supports IMS Voice. Oneexample of a reason that the registration might fail is because the SIPRegistrar does not allow it because of limitations in the subscriptionof the user. Another example of a reason is that the IMS registrationfails due to dropped messages or a delay in receiving messages. If theIMS registration fails, and the UE does nothing and remains EPS attachedbut not IMS registered for voice services, then no IMS voicesessions—mobile originated or mobile terminated—can be realized. Thissame situation may exist if the SIP registration succeeded however theindicator in the request for voice services was not allowed (that is,the requested indicator for voice was not returned in the SIP 200 OKresponse to the SIP Register Request). In this case, the UE may beregistered in IMS for the use of some services but may not be allowed touse this registration for transmitting voice media.

Example 1

In some implementations, the UE is configured to address this problem byrecognizing a situation where IMS registration for voice has failed, theUE's voice setting is set to “IMS Voice Preferred, CS Voice Secondary”.Upon recognizing this situation, the UE is configured to immediatelyattempt a combined registration procedure. This will then allow the UEto obtain voice services by means of CSFB if this is supported. If thecombined registration procedure fails, then the UE considers the UE'susage setting. If the UE's usage setting is “Voice Centric” or “DataCentric”, then the UE selects another RAT in which it may obtain voiceservices. If the UE's usage setting is “Data Only”, then the UE stays inthe current RAT (i.e. E-UTRAN) without access to voice services.

FIG. 3A shows a detailed flowchart of an example implementation for thiscase. The figure differs from FIG. 2A in that if IMS registration failsfollowing triggering of IMS registration in block 2A-1, as indicated at30, then processing continues in block 1A-5 with the performance of acombined registration procedure for CSFB as in TS 23.272. In addition,block 1A-8 (staying in the current RAT) is performed if the UE is “dataonly” (as indicated at 32), and block 1A-9 is performed (UE selectsanother RAT) if the UE is “voice centric” or “data centric” (asindicated at 34).

FIG. 3B shows a detailed flowchart of an example implementation for thecase where the UE's voice setting is set to “IMS PS voice only”. Thefigure differs from FIG. 2B in that if IMS registration fails followingtriggering of IMS registration in block 2B-1, as indicated at 36, thenthe UE checks the UE's usage setting at block 1B-5. If the UE's usagesetting is “Data Only” (as indicated at 38), then the UE stays inE-UTRAN and will not have access to voice services in block 1B-6. If theUE's usage setting is “Voice centric” or if the UE's usage setting is“Data Centric” (as indicated at 40), then the UE selects another RAT inwhich it may obtain voice services in block 1B-7.

Example 2A

In some implementations, the UE is configured to address this problem byrecognizing a situation where IMS registration for voice services hasfailed and the UE's usage setting is “Data Only”. Upon recognizing thissituation, the UE is configured to stay in EPS where the best PSservices can be provided. More specifically, the UE stays in E-UTRAN(the “current RAT” in the figures) and does not select another RAT. Thebest PS services can be provided in E-UTRAN. PS Services can also beprovided in GERAN/UTRAN but they are provided in a less optimized mannerin these RATs. The UE does not perform a combined registration attempt,but instead the UE is configured to retry the IMS registration procedurefor voice services. It is noted that the UE may have successfullyregistered with IMS for other services but may have been denied accessto voice services, as described above, and in this event, the UE retriesthe IMS registration procedure for voice services. In someimplementations, this is a single retry. In other implementations thereare multiple retries which may, for example, be periodically executed.

An example of this behavior is depicted in FIGS. 4A and 4B. Referringfirst to FIG. 4A, FIG. 4A is the same as FIG. 2A with the exception ofthree differences:

the UE performs one or more retries at 50 after IMS registration hasfailed;

block 1A-8 is executed following block 1A-7 if the UE's usage setting is“data only” (indicated at 52);

block 1A-9 is executed following block 1A-7 if the UE's usage setting is“voice centric” or “data centric” (indicated at 54).

Referring now to FIG. 4B, FIG. 4B is the same as FIG. 2B with theexception of three differences:

the UE performs one or more retries at 56 after IMS registration hasfailed;

block 1B-6 is executed following block 1B-5 if the UE's usage setting is“data only” (indicated at 58);

block 1B-7 is executed following block 1B-5 if the UE's usage setting is“voice centric” or “data centric” (indicated at 60).

Example 2C

In some implementations if the combined attach procedure described inexample 1 above fails, and the UE's usage setting is “Data Only”, the UEnotifies the user (via the user interface or some other alert) thatvoice services are unavailable. For example, if voice services cannot berealized, an indicator may be presented to the user. Any indicator tothe user (displayed, audio, vibrating, are just some examples) could beused to convey to the user that voice services are not currently able tobe provided even though the UE is in a coverage area.

An example of this behavior is depicted in FIG. 5A which is the same asFIG. 2A with the following differences:

upon IMS registration failure at 70 following an IMS registrationattempt, the UE performs a combined TAU at block 1A-5;

after block 1A-7, if the UE's usage setting is “data only” (as indicatedat 72), the UE notifies the user that voice services are not availableat block 5A-1 and the UE stays in the current RAT;

block 1A-9 follows block 1A-7 if the UE's usage setting is “voicecentric” or “data centric” (as indicated at 74).

Another example of this behavior is depicted in FIG. 5B which is thesame as FIG. 2B with the following differences:

upon IMS registration failure at 71 following an IMS registrationattempt, the UE checks the UE's Usage Setting for “Voice Centric” or“Data Centric” in block 1B-5;

after block 1B-5, if the UE's usage setting is “data only” (as indicatedat 73), the UE notifies the user that voice services are not availableat block 5B-1 and the UE stays in the current RAT;

block 1B-7 follows block 1B-5 if the UE's usage setting is “voicecentric” or “data centric” (as indicated at 75).

Upon being notified that voice services are not available, the user maychoose to change the UE's usage setting to “Voice Centric” or “DataCentric”. As the UE has already attempted a combined registrationprocedure and the attempt failed then the change of the UE's usagesetting to “Voice Centric” or “Data Centric” will cause the UE toselects to another RAT (such as GERAN/UTRAN) which could provide voice.

In some implementations, the notification to the user that voiceservices are not available also includes a prompt asking the user ifthey would like to change the UE's usage setting in order be obtainvoice service.

An example of this behavior is depicted in FIG. 6A. FIG. 6A is the sameas FIG. 5A with the following differences:

after block 5A-1, if the user accepts “data only” (indicated at 82),then the UE stays in the current RAT at block 1A-8;

after block 5A-1, if the user changes the UE's usage setting to “voicecentric” or “data centric” (indicated at 84), then the UE selectsanother RAT at block 1A-9.

In some implementations, when the UE's usage setting is changed from“data centric” to “voice centric,” the UE provides an indication to theAS to select GERAN or UTRAN radio access technology rather than E-UTRANfor the selected PLMN or equivalent PLMN. For example, such a processmay be completed after the UE receives EMM cause value #18.

Another example of this behavior is depicted in FIG. 6B. FIG. 6B is thesame as FIG. 5B with the following differences:

after block 5B-1, if the user accepts “data only” (indicated at 100),then the UE stays in the current RAT at block 1B-6;

after block 5B-1, if the user changes the UE's usage setting to “voicecentric” or “data centric” (indicated at 102), then the UE selectsanother RAT at block 1A-9.

Example 2D

In the case where the UE's voice setting is “IMS Voice Preferred, CSVoice Secondary” and where the UE's usage setting is set to “Data only”,when IMS Registration fails after one or more retries and a combinedregistration procedure is not automatically attempted, or in the casewhere the UE's voice setting is “IMS PS Voice Only” and the UE's usagesetting is set to “Data only”, then the UE is configured to notify theuser (via the user interface or some other alert) that voice servicesare unavailable. In this case the user may choose to change the UE'susage setting to “Voice Centric” or “Data Centric”. This immediatelyprompts the UE to attempt a combined registration procedure (in the casewhere the UE's voice setting is “IMS Voice Preferred, CS VoiceSecondary”), which, if successful, would allow the UE to remain in EPSuntil voice services are required, and in that case to obtain voiceservices by means of CSFB. In the case where the UE's voice setting is“IMS PS Voice Only”, the user may change the UE's usage setting to“Voice Centric” or “Data Centric” which would prompt the UE to reselectto another RAT that may support voice services.

An example of this behavior is depicted in FIG. 7A. FIG. 7A differs fromFIG. 2A in that:

following IMS registration failure (112), the UE notifies the user thatVoice Services are not available in block 7A-1;

if the user indicates “Voice Centric” or “Data Centric” (116), then themethod continues at Block 1A-5;

if the user indicates “Data only”, then IMS registration is not retried(114) and then the method continues at block 1A-8;

block 1A-9 follows block 1A-7 in the case (118) the UE's usage settingis “Voice Centric” or “Data Centric”.

Another example of this behavior is depicted in FIG. 7B. FIG. 7B differsfrom FIG. 2B in that:

following IMS registration failure (122), the UE notifies the user thatVoice Services are not available in block 7B-1;

if the user indicates “Voice Centric” or “Data Centric” (124), then themethod continues at Block 1B-5;

if the user indicates “Data only”, and IMS registration is not retried(128), then the method continues at block 1B-6;

block 1B-9 follows block 1B-5 in the case (126) the UE's usage settingis “Voice Centric” or “Data Centric”.

Example 2E

As a follow-on to example 2D, in some implementations, the user isprompted that IMS registration (original or some number of attempts) hasfailed, and the user could alternatively request “Retry of IMSRegistration for Voice”, which could prompt the UE leave the UE's usagesetting set to “Data Centric” or “Voice Centric” but to restart periodicattempts at IMS registration until successful or until a certain numberof tries had been attempted and failed. Alternatively the user couldindicate “Data Only” in which case the UE would leave the UE's usagesetting set to “Data Centric” and the UE will not reattempt IMSregistration (for the purpose of voice services).

An example of this behavior is depicted in FIG. 7C. FIG. 7C differs fromFIG. 7A in that:

following IMS registration failure (112), the UE notifies the user thatVoice Services are not available in block 7A-1 and if the user indicates“RETRY” at 110, then the method continues at block 2A-1.

Another example of this behavior is depicted in FIG. 7D. FIG. 7D differsfrom FIG. 7C in that:

following IMS registration failure (122), the UE notifies the user thatVoice Services are not available in block 7B-1, if the user indicates“RETRY” at 120, then the method continues at block 2A-1.

Example 3A

In some implementations, the UE is configured to recognize a situationwhere IMS registration has failed, and the UE's usage setting is “VoiceCentric”. The UE is configured to, upon recognizing this situation andregardless of whether the UE's voice setting is “IMS PS voice only” or“IMS Voice Preferred, CS Voice Secondary”, trigger the AS toselect/reselect to another RAT (the target RAT) in which voice servicescan be realized (e.g. GERAN/UTRAN).

A first detailed example of this behavior is depicted in FIG. 8A. FIG.8A differs from FIG. 2A as follows:

following IMS registration failure at 130, the UE checks the UE's usagesetting for “Voice Centric” or “Data Centric” at block 8A-1;

If the setting is “Data Centric” or “Data Only” as indicated at 132, themethod continues at block 1A-5;

If the setting is “Voice Centric” as indicated at 138, then the methodcontinues at block 1A-9 with selection of another RAT;

Block 1A-8 follows block 1A-7 for the case the UE's usage setting is“Data only” (indicated at 134);

Block 1A-9 follows block 1A-7 for the case where the UE's usage settingis “Voice Centric” or “Data Centric” (indicated at 136).

A second detailed example of this behavior is depicted in FIG. 8B. FIG.8B differs from FIG. 2B as follows:

-   -   following IMS registration failure at 140, the UE checks the        UE's usage setting for “Voice Centric” or “Data Centric” at        block 8B-1;

If the setting is “Data Only” as indicated at 142, the method continuesat block 1B-6;

-   -   If the setting is “Voice Centric” or “Data Centric” as indicated        at 144, then the method continues at block 1B-7 with selection        of another RAT;    -   Block 1B-6 follows block 1B-5 for the case where the UE's usage        setting is “Data Only” (indicated at 146);

Block 1B-7 follows block 1B-5 for the case where the UE's usage settingis “Voice Centric” or “Data Centric” (indicated at 148).

Example 3B

In some implementations, the UE is configured to, as a follow on to RATreselection as described with reference to example 3A above, retry IMSregistration once it is in the target system if it learns that thetarget system can support IMS voice. If this subsequent attempt at IMSRegistration in the target system fails, then in this case the UE mayobtain voice services via CS in the target system.

A first example of this behavior is depicted in FIG. 9A which is thesame as FIG. 8A with the addition of blocks 9A-1, 9A-2 and 9A-3.Following block 1A-9, the UE retries IMS registration for voice if itlearns that the target system can support IMS voice at block 9A-1. Ifthere is success, then the UE obtains voice services via PS in thetarget system at block 9A-2. If there is failure, then the UE obtainsvoice services via CS in the target system at block 9A-3.

A second example of this behavior is depicted in FIG. 9B which is thesame as FIG. 8B with the addition of blocks 9B-1, 9B-2 and 9B-3.Following block 1B-7, the UE retries IMS registration for voice if itlearns that the target system can support IMS voice at block 9B-1. Ifthere is success, then the UE obtains voice services via PS in thetarget system at block 9B-2. If there is failure, then the UE obtainsvoice services via CS in the target system at block 9B-3.

Third Problem: UE May Be Constrained in an Inappropriate RAT

A third problem with the behavior specified in FIGS. 1A and 1B is thatthe UE may become constrained in an inappropriate RAT. Morespecifically, if the UE's usage setting in FIGS. 1A and 1B is set to“Data Centric”, this can lead to that UE not getting voice services atall. If “Data Centric” in FIGS. 1A and 1B is taken to mean that the UEonly wants data services (even if that precludes ANY voice service),i.e. “Data Only”, then this is not a problem. In the case where “datacentric” in FIGS. 1A and 1B is taken to mean “Data Centric” as definedabove in this document, then this behavior is problematic.

Furthermore, if the UE stays in the current RAT and does not have accessto voice services because the network VoIMS indication (in theregistered tracking area, since this indication is per tracking area)did not indicate support, but due to mobility the UE enters a routingarea of GERAN/UTRAN radio coverage or tracking area of E-UTRAN coveragewhere the network VoIMS indicator does indicate that IMS PS Voice issupported, then the UE needs to subsequently re-attempt the IMSregistration for voice.

In another situation, if the UE's voice setting is “IMS PS Voice Only”or “IMS Voice Preferred, CS Voice Secondary”, and the UE's usage settingis set to “Voice Centric” or “Data Centric”, the UE may end up campingin GERAN/UTRAN and use CS voice services for voice even if voiceservices over IMS in LTE or GERAN/UTRAN may be become available due tothe mobility of the UE. As the UE moves, it may move into the coveragearea of a new E-UTRAN tracking area or a new GERAN/UTRAN routing areawhich does support IMS Voice, in which case there is a possibility thatthe UE could get IMS voice services over GERAN/UTRAN or over LTE, andfor a “data centric” UE better PS service over LTE, if it were notconstrained in GERAN/UTRAN.

Example 1

In some implementations, the UE is configured to recognize a situationin which the UE's usage setting is set to “Data Only”, the UE's voicesetting is “IMS PS Voice Only” or “IMS Voice Preferred, CS VoiceSecondary” and in which when it tried to EPS attach, it learned that“IMS Voice over PS session not supported”, such that the UE ends upcamping in E-UTRAN with no access to voice services. The support of IMSVoice over PS session is per Tracking Area (TA). The UE is configured tothen monitor the TA of neighboring E-UTRAN cells until a cell with adifferent TA/RA (or alternatively a cell with a TA outside the UE TAIList) is detected. Upon detecting such an LTE cell, the UE attempts tocamp on this cell, and sends a Tracking Area Update to the network aspart of this process. In response to this, the UE receives a TrackingArea Update response. The Tracking Area Update response includes thenetwork VoIMS Indicator for this tracking area. If the indicator is “IMSVoice over PS session supported”, then the UE retries the IMSregistration with indicators requesting voice services. Follow onbehavior may for example be in accordance with the implementationsdescribed above which deal with IMS registration failure

An example of this behavior is depicted in FIG. 10A. When the UE arrivesat block 1A-8, the scenario described above may occur. The methodcontinues in block 10A-1 with the UE monitoring the TA of neighboringE-UTRAN cells until a cell with a different TA (or alternatively a cellwith a TA outside the UE TAI List) is detected. In block 10A-2, upondetecting such a cell, the UE attempts to camp on this cell, and sends aTracking Area Update to the network as part of this process. In responseto this, the UE receives a Tracking Area Update response. The TrackingArea Update response includes the network VoIMS Indicator for thistracking area. If the indicator is “IMS Voice over PS session supported”(block 10A-3), then the UE retries the IMS registration with indicatorsrequesting voice services in block 10A-4. Follow on behavior may forexample be in accordance with the implementations described above whichdeal with IMS registration failure. For a UE voice setting of IMS PSvoice only, steps 10A-1, 10A-2, 10A-3 and 10A-4 would follow block 1B-6of FIG. 2B.

Example 2

In some implementations, the UE is configured to recognize a situationin which the UE's usage setting is set to “Voice Centric” or “DataCentric”, the UE's voice setting is “IMS PS Voice Only” or “IMS VoicePreferred, CS Voice Secondary”, and when it tried to EPS attach, itreceives the VoIMS Indicator and learns that “IMS Voice over PS sessionnot supported”, such that it ends up camping in GERAN/UTRAN with voiceservice but suboptimal data services. In this case, when the UE is inidle mode, the UE is configured to attempt (once, or multiple times, forexample at regular intervals, or based on a timer) to reselect to asuitable found E-UTRAN cell. As described above, this process triggers aregular tracking area update when the UE's voice setting is “IMS PSVoice Only” or a combined tracking area update if the UE's voice settingis “IMS Voice Preferred, CS Voice Secondary”. If the VoIMS Indicatorobtained during the TAU or combined TA/LA Update Procedure indicatesthat IMS voice is supported, then the UE proceeds to try IMSregistration with indicators requesting voice services. Follow onbehavior may for example be in accordance with the implementationsdescribed above which deal with IMS registration failure.

An example of this behaviour for UE Voice Setting of “IMS PS Voice Only”is depicted in FIG. 10B. When the UE arrives at block 1B-7, the scenariodescribed above may occur. In this case, when the UE is in idle mode,the UE is configured to attempt (once, or multiple times, for example atregular intervals, or based on a timer) to reselect to a suitable foundE-UTRAN cell at block 10B-1. This process triggers a regular trackingarea update when the UE's voice setting is “IMS PS Voice Only” or acombined tracking area update if the UE's voice setting is “IMS VoicePreferred, CS Voice Secondary”. If the VoIMS Indicator obtained duringthe TAU or combined TA/LA Update Procedure indicates that IMS voice issupported, then the UE proceeds to try IMS registration with indicatorsrequesting voice services at 10B-2. For a UE Voice Setting of “IMS VoicePreferred, CS Voice Secondary”, steps 10B-1 and 10B-2 would follow block1A-9 of FIG. 2A.

[Another example is depicted in FIG. 10C. When the UE arrives at block1A-9, the scenario described above may occur. The method continues inblock 10C-1 where the UE determines that the RA of the current cell isdifferent from the previous RA. In block 10C-2, upon detecting such acell, the UE sends a Routing Area Update to the network as part of thisprocess. In response to this, the UE receives a Routing Area Updateresponse. The Routing Area Update response includes the network VoIMSIndicator for this routing area. If the indicator is “IMS Voice over PSsession supported” (block 10C-3), then the UE retries the IMSregistration with indicators requesting voice services in block 10C-4.Follow on behavior may for example be in accordance with theimplementations described above which deal with IMS registrationfailure. For a UE voice setting of IMS PS voice only, steps 10C-1,10C-2, 10C-3 and 10C-4 would follow block 1B-6 of FIG. 2B.

In some implementations, a combined routing area update procedure may beinitiated by a GPRS MS operating in MS operation modes A or B, when theMS is in state GMM-REGISTERED and MM-IDLE, when the network operates innetwork operation mode I, and when, in Iu mode, the UE receives anindication from the upper layers that the SIP registration to the IPMultimedia subsystem has failed and the UE's usage setting is “VoiceCentric.”

One aspect of the possible examples described for problem 3 is that theUE obtains the VoIMS indicator for the TA or RA by performing a NASregistration procedure such as a Tracking Area Update or Routing AreaUpdate. This registration procedure requires signalling between the UEand the network. For example, a NAS registration response message may bea response to an EPS attach procedure, a TRACKING AREA UPDATE response,a ROUTING AREA UPDATE response, an ATTACH ACCEPT response, or a TRACKINGAREA UPDATE ACCEPT response. In some implementations, the network isconfigured to broadcast the VoIMS indicator as part of the broadcastsystem information sent by every cell. As an example of how this VoIMSindicator could be used can be considered as a minor variation of theimplementation described in FIG. 10B. Instead of the UE attempting toreselect to an E-UTRAN cell at regular intervals and perform TrackingArea Update to obtain the VoIMS indicator (as shown in Block 10B-1 ofFIG. 10B), the UE could attempt to read broadcast system information ofan E-UTRAN cell at regular intervals to obtain the VoIMS indicator. Ifthe VoIMS Indicator obtained broadcast system information indicates thatIMS voice is supported, then the UE proceeds to try IMS registrationwith indicators requesting voice services at 10B-2

Fourth Problem: Change Back to “Voice Centric” or “Data Centric” afterthe UE's Usage Setting has been Changed to “Data Only”

A fourth problem with the behaviour specified in the above-referencedFIGS. 1A and 1B is that in some situations it is desirable for the UE'sUsage Setting to be changed. For example, if the UE is downloading alarge volume of data then it may be desirable for the UE's Usage Settingto be “Data only” so that the UE uses E-UTRAN even if voice services arenot available on E-UTRAN. When the download of the large volume of datais complete then it may be desirable for the UE's Usage Setting to be“Voice Centric” or “Data Centric” again in order to ensure that voice isavailable, even it is means that another RAT is selected. A particularproblem is that the user may set the UE's Usage Setting to be “dataonly” but then forget to revert the setting back to “Voice Centric” or“Data Centric” at a later stage.

Example 1

More specifically, if the UE's usage setting in the above-referencedFIG. 1A or 1B is set to “Data Centric”, based on user preferences orbased on the requirements of the applications running in the UE, the UEusage setting may be modified to “Data Only” to give priority to dataservices and therefore have the UE select the best RAT for data services(i.e. E-UTRAN). However, it is desirable that the UE Usage Setting canbe modified at a later time to the original value (i.e. “Voice Centric”or “Data Centric”). As an example, the UE Usage Setting may be changedby the user at a later time. In another example, an application runningin the UE and requires the best PS service available even when the UE is“Voice Centric” or “Data Centric”, and based on this the application orthe user changes the UE Usage Setting to “Data Only”. However, once theapplication has terminated, the application or the UE change the UEUsage Setting back to the original value, that is “Voice Centric” or“Data Centric”.

In such scenarios, once the UE Usage Setting is changed to “Data Only”the UE will end up selecting the RAT based on the behavior described inthe implementations above for a “Data Only” UE. However, once the UEUsage Setting is modified back to the original value, the UE should tryto connect to the appropriate RAT and attempt to access voice servicesbased on the availability of IMS and the UE Voice Setting of the UE.With the current behavior defined for the UE, however, the UE would notattempt to reselect an appropriate RAT nor to register for IMS when IMSis available.

In certain scenarios, the UE Usage Setting is modified by the user or anapplication (or set of applications) running in the UE from “DataCentric” or “voice Centric” to “Data Only” to allow for the best PSservice for applications running in the UE. At a later time, the UEUsage Setting is reverted to the original setting based a set ofpossible triggering conditions. As a result, the UE based on the UEVoice Settings performs one or more of the procedures described in theimplementations above to discover whether IMS voice is available,register with IMS and select the appropriate RAT.

With reference to FIG. 11A, in an implementation, an application (or setof applications) running in the UE modifies UE Usage Setting at block11A-1. In block 11A-2, the application(s) that modified the UE UsageSetting terminates (or alternatively, the application(s) need for “dataonly” operation comes to an end) and causes the UE Usage setting to berestored to the original value. If the UE Voice Setting is “IMS VoicePreferred, CS Voice secondary”, the UE will behave as in theimplementations above for an UE whose UE Voice Setting is “IMS VoicePreferred, CS Voice secondary”. If the UE Voice Setting is “IMS PS Voiceonly”, the UE will behave as in the implementations above for UE whoseUE Voice Setting is “IMS PS Voice only”. This is generally indicated atblock 11A-3.

With reference to FIG. 11B, in an implementation, the user requests amobile originated voice call in block 11B-1. On request of the mobileoriginated voice call the UE reverts to “Voice Centric” or “DataCentric” in order to be able to establish the voice call in block 11B-2.The UE then behaves as in the implementation of FIG. 11A depending onthe UE Voice Setting. This involves reverting to the original UE UsageSetting in block 11B-3, and then continuing with one of the previouslydescribed methods (11B-4).

With reference to FIG. 11C, in an implementation, the UE receives anemail with a voicemail as an attachment in block 11C-1. On reception ofthis email the UE reverts to “Voice Centric” or “Data Centric” in orderto be able to return the missed call in block 11C-2. The UE then behavesas in the implementation of FIG. 11A depending on the UE Voice Setting.This involves reverting to the original UE Usage Setting in block 11C-3,and then continuing with one of the previously described methods(11C-4).

With reference to FIG. 11D, in an implementation, the user receives anSMS indication that a voice mail is waiting or that a call has beenmissed in block 11D-1. On reception of this SMS the UE reverts to “VoiceCentric” or “Data Centric” in order to be able to establish a voice callto retrieve the voice mail and/or return the missed call. The UE thenbehaves as in the implementation of FIG. 11A depending on the UE VoiceSetting. This involves reverting to the original UE Usage Setting inblock 11D-3, and then continuing with one of the previously describedmethods (11D-4).

With reference to FIG. 11E, in an implementation, an incoming IMS voicecall was received by the IMS infrastructure but the voice call could notbe delivered to the UE because the IMS Registration for IMS Voice hadnot been successful, and the UE receives notification from IMS of suchmissed call in block 11E-1. On reception of this notification the UEreverts to “Voice Centric” or “Data Centric” in order to be able toreturn the missed voice call at block 11E-2. The UE then behaves as inthe implementation of FIG. 11A depending on the UE Voice Setting. Thisinvolves reverting to the original UE Usage Setting in block 11E-3, andthen continuing with one of the previously described methods (11E-4).

In all the implementations above the restoration can be achieved as anexample by storing the original UE Usage Setting value when it ismodified by the application or the user and retrieving the value.

Another Mobile Device

Referring now to FIG. 12, shown is a block diagram of a mobilecommunication device 700 that may implement UE related methods describedherein. It is to be understood that the mobile device 700 is shown withvery specific details for example purposes only.

A processing device (a microprocessor 728) is shown schematically ascoupled between a keyboard 714 and a display 726. The microprocessor 728controls operation of the display 726, as well as overall operation ofthe mobile device 700, in response to actuation of keys on the keyboard714 by a user.

The mobile device 700 has a housing that may be elongated vertically, ormay take on other sizes and shapes (including clamshell housingstructures). The keyboard 714 may include a mode selection key, or otherhardware or software for switching between text entry and telephonyentry.

In addition to the microprocessor 728, other parts of the mobile device700 are shown schematically. These include: a communications subsystem770; a short-range communications subsystem 702; the keyboard 714 andthe display 726, along with other input/output devices including a setof LEDS 704, a set of auxiliary I/O devices 706, a serial port 708, aspeaker 711 and a microphone 712; as well as memory devices including aflash memory 716 and a Random Access Memory (RAM) 718; and various otherdevice subsystems 720. The mobile device 700 may have a battery 721 topower the active elements of the mobile device 700. The mobile device700 is in some implementations a two-way radio frequency (RF)communication device having voice and data communication capabilities.In addition, the mobile device 700 in some implementations has thecapability to communicate with other computer systems via the Internet.

Operating system software executed by the microprocessor 728 is in someimplementations stored in a persistent store, such as the flash memory716, but may be stored in other types of memory devices, such as a readonly memory (ROM) or similar storage element. In addition, systemsoftware, specific device applications, or parts thereof, may betemporarily loaded into a volatile store, such as the RAM 718. In someimplementations, one or more parameters representative of unevenness inthe signal constellation are stored in the non-volatile memory or in avolatile store. Communication signals received by the mobile device 700may also be stored to the RAM 718.

The microprocessor 728, in addition to its operating system functions,enables execution of software applications on the mobile device 700. Apredetermined set of software applications that control basic deviceoperations, such as a voice communications module 730A and a datacommunications module 730B, may be installed on the mobile device 700during manufacture. In addition, a personal information manager (PIM)application module 730C may also be installed on the mobile device 700during manufacture. The PIM application is in some implementationscapable of organizing and managing data items, such as e-mail, calendarevents, voice mails, appointments, and task items. The PIM applicationis also in some implementations capable of sending and receiving dataitems via a wireless network 710. In some implementations, the dataitems managed by the PIM application are seamlessly integrated,synchronized and updated via the wireless network 710 with the deviceuser's corresponding data items stored or associated with a hostcomputer system. As well, additional software modules, illustrated asother software module 730N, may be installed during manufacture.

Communication functions, including data and voice communications, areperformed through the communication subsystem 770, and possibly throughthe short-range communications subsystem 702. The communicationsubsystem 770 includes a receiver 750, a transmitter 752 and one or moreantennas, illustrated as a receive antenna 754 and a transmit antenna756. In addition, the communication subsystem 770 also includes aprocessing module, such as a digital signal processor (DSP) 758, andlocal oscillators (LOs) 760. The specific design and implementation ofthe communication subsystem 770 is dependent upon the communicationnetwork in which the mobile device 700 is intended to operate. Forexample, the communication subsystem 770 of the mobile device 700 may bedesigned to operate with the Mobitex™, DataTAC™ or General Packet RadioService (GPRS) mobile data communication networks and also designed tooperate with any of a variety of voice communication networks, such asAdvanced Mobile Phone Service (AMPS), Time Division Multiple Access(TDMA), Code Division Multiple Access (CDMA), Personal CommunicationsService (PCS), Global System for Mobile Communications (GSM), etc. Othertypes of data and voice networks, both separate and integrated, may alsobe utilized with the mobile device 700. The particular devices underconsideration here are multi-mode mobile devices, and as such theyinclude hardware and/or software for implementing at least two RATs.More specifically, in a particular example, there would be a respectivecommunication subsystem 770 for each RAT implemented by the device.

Network access may vary depending upon the type of communication system.For example, in the Mobitex™ and DataTAC™ networks, mobile devices areregistered on the network using a unique Personal Identification Number(PIN) associated with each device. In GPRS networks, however, networkaccess is typically associated with a subscriber or user of a device. AGPRS device therefore typically has a subscriber identity module,commonly referred to as a Subscriber Identity Module (SIM) card, inorder to operate on a GPRS network.

When network registration or activation procedures have been completed,the mobile device 700 may send and receive communication signals overthe communication network 710. Signals received from the communicationnetwork 710 by the receive antenna 754 are routed to the receiver 750,which provides for signal amplification, frequency down conversion,filtering, channel selection, etc., and may also provide analog todigital conversion. Analog-to-digital conversion of the received signalallows the DSP 758 to perform more complex communication functions, suchas demodulation and decoding. In a similar manner, signals to betransmitted to the network 710 are processed (e.g., modulated andencoded) by the DSP 758 and are then provided to the transmitter 752 fordigital to analog conversion, frequency up conversion, filtering,amplification and transmission to the communication network 710 (ornetworks) via the transmit antenna 756.

In addition to processing communication signals, the DSP 758 providesfor control of the receiver 750 and the transmitter 752. For example,gains applied to communication signals in the receiver 750 and thetransmitter 752 may be adaptively controlled through automatic gaincontrol algorithms implemented in the DSP 758.

In a data communication mode, a received signal, such as a text messageor web page download, is processed by the communication subsystem 770and is input to the microprocessor 728. The received signal is thenfurther processed by the microprocessor 728 for an output to the display726, or alternatively to some other auxiliary I/O devices 706. A deviceuser may also compose data items, such as e-mail messages, using thekeyboard 714 and/or some other auxiliary I/O device 706, such as atouchpad, a rocker switch, a thumb-wheel, or some other type of inputdevice. The composed data items may then be transmitted over thecommunication network 710 via the communication subsystem 770.

In a voice communication mode, overall operation of the device issubstantially similar to the data communication mode, except thatreceived signals are output to a speaker 711, and signals fortransmission are generated by a microphone 712. Alternative voice oraudio I/O subsystems, such as a voice message recording subsystem, mayalso be implemented on the mobile device 700. In addition, the display716 may also be utilized in voice communication mode, for example, todisplay the identity of a calling party, the duration of a voice call,or other voice call related information.

The short-range communications subsystem 702 enables communicationbetween the mobile device 700 and other proximate systems or devices,which need not necessarily be similar devices. For example, theshort-range communications subsystem may include an infrared device andassociated circuits and components, or a Bluetooth™ communication moduleto provide for communication with similarly-enabled systems and devices.

Numerous modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein.

What is claimed is:
 1. A method in a User Equipment (UE), the methodcomprising: receiving a Non Access Stratum (NAS) protocol Accept messagewith a first indicator indicating that an IMS voice over packet-switchedsession is supported, the first indicator being provided by lower layersof the UE to upper layers of the UE; responsive to the first indicator,performing an attempt to register with an Internet Protocol MultimediaSubsystem (IMS); and based on a failure of the attempt to register withthe IMS, performing, by the UE, a combined tracking area update (TAU).2. The method of claim 1, wherein the NAS protocol Accept message is anATTACH accept message.
 3. The method of claim 1, wherein the NASprotocol Accept message is a TRACKING AREA UPDATE ACCEPT message.
 4. Anon-transitory computer readable medium storing instructions that, whenexecuted, cause a User Equipment (UE) to: receive a Non Access Stratum(NAS) protocol Accept message with a first indicator indicating that anIMS voice over packet-switched session is supported, the first indicatorbeing provided by lower layers of the UE to upper layers of the UE;responsive to the first indicator, attempt a registration with anInternet Protocol Multimedia Subsystem (IMS); and based on a failure ofthe attempt to register with the IMS, performing, by the UE, a combinedtracking area update (TAU).
 5. The non-transitory computer readablemedium of claim 4, wherein the NAS protocol Accept message is an ATTACHaccept message.
 6. The non-transitory computer readable medium of claim4, wherein the NAS protocol Accept message is a TRACKING AREA UPDATEACCEPT message.
 7. A User Equipment (UE) comprising a processorconfigured to: receive a Non Access Stratum (NAS) protocol Acceptmessage with a first indicator indicating that an IMS voice overpacket-switched session is supported, the first indicator being providedby lower layers of the UE to upper layers of the UE; responsive to thefirst indicator, perform an attempt to register with an InternetProtocol Multimedia Subsystem (IMS); and based on a failure of theattempt to register with the IMS, perform a combined tracking areaupdate (TAU).
 8. The UE of claim 7, wherein the NAS protocol Acceptmessage is an ATTACH accept message.
 9. The UE of claim 7, wherein theNAS protocol Accept message is a TRACKING AREA UPDATE ACCEPT message.10. A User Equipment (UE), comprising a processor configured to: receivea Non Access Stratum (NAS) protocol Accept message with a firstindicator indicating that an IMS voice over packet-switched session issupported, the first indicator being provided by lower layers of the UEto upper layers of the UE; responsive to the first indicator, perform anattempt to register with an Internet Protocol Multimedia Subsystem(IMS); and based on a failure of the attempt to register with the IMS,perform, by the UE, a selection to another radio access technology(RAT).
 11. The UE of claim 10, wherein the first indicator is a IMSvoice over packet-switched session (IMS VoPS) indicator.
 12. The UE ofclaim 10, wherein the NAS protocol Accept message is an ATTACH acceptmessage.
 13. The UE of claim 10, wherein the NAS protocol Accept messageis a TRACKING AREA UPDATE ACCEPT message.